CPC G02B 27/0172 (2013.01) [G02B 6/34 (2013.01); G02B 2027/0123 (2013.01); G02B 2027/0178 (2013.01)] | 13 Claims |
1. A diffractive optical waveguide for optical pupil expansion, comprising:
a waveguide substrate;
a coupling-out grating disposed on or in the waveguide substrate and configured to couple input light out of the waveguide substrate by diffraction, wherein,
the coupling-out grating comprises a plurality of grating lines with widths; the plurality of grating lines are spaced in a cycle of a first predetermined period along a first direction and are spaced in a cycle of a second predetermined period along a second direction; each of the grating lines comprises a plurality of periodic structures in continuous and connected arrangement,
wherein, each of the periodic structures comprises a first edge and a second edge spaced apart in the first direction; the first predetermined period is defined as the distance between the first edge and the second edge in the first direction; the width of the first edge is equal to the width of the second edge; the width of the first edge and the width of the second edge are each smaller than the second predetermined period; the distance between the center of the first edge and the center of the second edge in the second direction is defined 0.5 times the second predetermined period,
each of the periodic structures further comprises a first side edge connecting the first edge and the second edge, and a second side edge connecting the first edge and the second edge; the first side edge is opposite to the second side edge; at least one of the first side edge and the second side edge is a non-linear side edge.
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